This invention relates generally to air valves and more particularly to an air valve designed to minimize icing and improve efficiency for a diaphragm pump or the like. Current diaphragm pumps, as well as other pneumatic devices, experience two problems: (1) icing which results in reduced/erratic performance of the pump, and (2) inefficiency resulting from oversized valve porting to overcome icing provided in current design.
The air motor valving used to control reciprocating motion in current designs handles both the feed air to the driving piston or diaphragm and exhaust air through the same porting. In order to obtain fast switch over and high average output pressure it is important the piston/diaphragm chambers are exhausted as quickly as possible. In order for this to occur the porting through the valve is made as large as possible. The large port area allows the air to exhaust rapidly however; in doing so large temperature drops are generated in the valve. Any water in the air will drop out and freeze. As with most valves the geometry of the flow path through the valve may contain areas where the flow may be choked followed by large expansions and stagnation areas. These are the areas where water collects and freezes.
The valving itself may also become extremely cold since exhaust air is continually flowing through the valve and may cause water in the incoming air to freeze.
The large port area required to dump the exhaust is also used to feed the air chamber. During the fill cycle the large porting allows the chamber to fill rapidly and reach a high mean effective pressure in the chamber at high cycle rates. The head pressures developed at high flow rates are relatively low which requires a finite chamber pressure and volume to move the fluid at the required flow rate and head. By sizing the inlet porting to meet flow requirements the volume of air required is reduced as well as the amount to exhaust.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.